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What causes lockjaw?

Apr 10, 2023Oral health, Oral Hygiene

What causes lockjaw?

Lockjaw is an issue that arises when a muscle remains in an active, contracted state and fails to relax (spasm). There are numerous possible causes for this muscular spasm that accompanies lockjaw.

A spasm may occur in response to an injury of the muscle, nerve, bone, tendon, or ligament. Additionally, it could be linked to health complications, bacterial infections, or medication use.

Temporomandibular Joint (TMJ) Disorders

The Temporomandibular Joint (TMJ) is located at the sides of the face situated below the eyes and close to the ears. This joint connects the associated muscles, bones, tendons, and ligaments that control the movement of the jaw.

The TMJ is responsible for facilitating a range of bodily functions, including chewing food, speaking, and yawning. Unfortunately, TMJ disorders are common chronic conditions that can potentially lead to lockjaw.

TMJ can develop due to a variety of causes, such as:

  • Arthritis
  • Inflammatory disease
  • Facial trauma

Even after the initial discomfort of temporomandibular joint (TMJ) disorder has subsided, the associated symptom of lockjaw can recur.

Oral Infections

Infections of the oral cavity or surrounding jaw muscles, such as peritonsillar abscesses, can interfere with normal movement of the jaw, resulting in lockjaw.

In rare cases, an infection can lead to permanent damage of nerve or muscle tissue. This can increase the chances of recurrent episodes of lockjaw.


Certain medications can cause nerve impairment, potentially resulting in lockjaw condition. Anti-nausea medications, such as metoclopramide (Reglan), and certain antipsychotic medications are the most common culprits of this effect.

In rare cases, anesthetics can cause a potentially life-threatening reaction known as malignant hyperthermia. Symptoms of this condition include a rapid increase in body temperature and heart rate, along with severe muscle spasms which may result in lockjaw.


Cancer and certain cancer treatments, such as surgery or radiation, may cause damage to the muscles of the jaw responsible for movement.

One should be aware of certain risk factors associated with the development of lockjaw during cancer treatment. These include:

  • Head or neck cancer
  • Surgery for head or neck cancer
  • Radiation treatment for head or neck cancers

Patients with a diagnosis of head or neck cancer, or who have been treated for these types of cancers, have an approximately 30% chance of developing lockjaw.


Tetanus is a bacterial infection caused by Clostridium tetani, which can enter the body through cuts and wounds. Puncture wounds and any other type of damaged skin are especially vulnerable to the infectious spores.

Individuals are at an increased risk of contracting tetanus when exposed to cuts and wounds of certain types, including:

  • Wounds that may be exposed to fecal, dirt, or saliva matter should be carefully monitored for signs of contamination.
  • Puncture wounds, which occur when a pointed object pierces the skin, can often be caused by rusted nails or needles.
  • Burns
  • Crush injuries
  • Injuries that cause dead tissue

In addition to wounds, tetanus can enter the body through other, less common means. These include:

  • Superficial wounds
  • Surgical wounds
  • Dental infections
  • Insect bites
  • Chronic sores or infections
  • Compound fractures
  • Intramuscular injections
  • IV drug use


What is Lockjaw?

Tetanus, often referred to as “lockjaw,” is an infection characterized by tightness in the muscles of the jaw, which can lead to difficulty speaking or opening the mouth.

In the United States, tetanus has become a rare occurrence largely due to the availability of the tetanus vaccine. In fact, it is so uncommon that there are only approximately 30 reported cases of lockjaw annually. Significantly, nearly all of these cases occur in individuals who have not been vaccinated against tetanus infection.

Tetanus is a serious health concern, as the muscle spasms it causes can quickly progress and become life-threatening. Initial symptoms are typically observed in the jaw, followed by a tightening and stiffness of other muscles. This can lead to difficulty breathing and may result in fatality if not treated promptly. If an individual has not received a tetanus vaccine or cannot recall when their last booster shot was given and has sustained an injury in an outdoor environment, it is imperative to seek medical attention for a tetanus booster injection. Failure to do so may lead to severe breathing problems and even be fatal.

Lockjaw, also known as Trismus, is a disorder of the jaw muscles characterized by muscle spasm of the mastication muscles that limits the opening of the mouth. Clinically, this disorder manifests as a limitation of jaw or mouth opening due to muscular spasm. It is generally accepted that any type of difficulty in opening the mouth or jaw, regardless of its cause, is referred to as lockjaw or trismus.

Lockjaw is a serious condition that can affect an individual’s ability to speak, eat, and maintain oral hygiene. It can either be temporary or permanent; however, temporary lockjaws are more common. In severe cases, it can even lead to permanent changes in facial appearance. Patients who experience a serious and painful oral condition may find even the simplest task of swallowing to be difficult. This painful condition can be especially challenging to diagnose due to the potential for limited or even impossible mouth openings.

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